The invention relates to a display instrument, in particular for a vehicle, having a housing which has a connection for a connection cable comprising a plurality of individual wires.
Such display instruments are provided in the dashboard of, for example, modern motor vehicles and watercraft and are generally known. They usually have on the rear side a connector receptacle, into which a connector of a connection cable is inserted for the contacting of the display instrument following installation of the respective display instrument. In motor vehicles, and even more so in ships, there is the risk that moisture can penetrate into the display instrument via such connector receptacles, built into the housing of a display instrument, and via the plug-in connection itself. Therefore, a cable length is often led out of the housing of such a display instrument in a sealing manner and is connected to a connection cable only outside the display instrument. This type of contacting likewise entails the risk that moisture can penetrate into the display instrument in the region of the cable bushing, in particular whenever the seal of the cable bushing has not been properly fitted or whenever tensile forces act on the cable length.
The invention is based on the problem of providing a display instrument of the type stated at the beginning in such a way that simplest possible contacting is possible without the risk of moisture penetrating into the display instrument arising.
This problem is solved according to the invention by a cable receptacle for a flat cable, as the connection cable, being arranged on the outside of the housing and by the housing having contact pins which are molded into it and protrude outward with contact tips from the housing into the cable receptacle.
In the case of such a display instrument, the housing can be made completely impervious without the use of seals on account of the encapsulated contact pins. Even tensile forces acting on the display instrument via the flat cable cannot lead to instances of unimperviousness, because no bores or clearances to be closed by seals are required in the housing for leading through the cable or the contact pins. The display instrument according to the invention is particularly well suited if the flat cable is a data bus line. In such cases, until now the respective display instruments had to have an input and an output. The xe2x80x9ctappingxe2x80x9d according to the invention of the individual wires of the cable by means of the contact tips allows a data bus line to be connected to the respective display instrument without the continuing data bus line being interrupted. A further advantage of the display instrument according to the invention is that the insulation of the individual wires of a flat cable provides a seal between the contact pins and the flat cable, with the result that no moisture can penetrate into the flat cable through the contacting.
A particularly advantageous development of the invention is that the housing has a base plate, closing the latter at the rear, and the cable receptacle is provided with the contact pins on the base plate. This embodiment is particularly simple to manufacture, because the base plate with the contact pins and the cable receptacle can be produced as a relatively simple injection molding in an injection mold.
The contact pins are held particularly firmly in the display instrument, without any major expenditure being required for this purpose, if a printed circuit board is arranged approximately parallel to the base plate in the interior of the housing and if the contact pins penetrate through the printed circuit board. By this type of design, the contact pins are fixed close to the two ends, on the one hand by the base plate, on the other hand by the printed circuit board. They therefore do not tend to break out from the base plate.
For the electrical connection of the contact pins and the printed circuit board, it is conceivable to use, for example, a clamped connection.
The contacting between the contact pins and the printed circuit board may, however, advantageously take place in a conventional and simple way with devices that are customarily present if the contact pins are soldered to the printed circuit board.
The flat cable can be pressed particularly easily onto the contact tips and held in the pressed-on position if the cable receptacle has a clamping clip which can be moved over the flat cable and presses the latter onto the contact tips.
The clamping clip could be held on the flat cable by one or two screw connections. The connection of the display instrument to the flat cable is possible particularly quickly if the cable receptacle has snap-in means for the snap-in engagement of the clamping clip in a closed position, clamping the flat cable.
A particularly secure and positionally accurate fixing of the clamping clip on the cable receptacle can be achieved if the clamping clip has a positioning bore and the cable receptacle has a corresponding positioning pin, gripping into the positioning bore when the clamping clip is closed.
Fitting mistakes caused by pole reversal of the connection cable can be excluded if the positioning pin of the cable receptacle can engage in a corresponding clearance of the flat cable. Such an embodiment additionally has the advantage that, when exchanging a display instrument, the contact tips inevitably go exactly into the holes left behind in the flat cable by the contact tips of the original display instrument. As a result, the flat cable is not left with any uninsulated regions.
It helps to minimize further the manufacturing costs of the display instrument according to the invention if the clamping clip is connected to the base plate in such a way that it can swivel by means of a film hinge.
The positioning pin can grip into the positioning bore without undesirably great backlash from the outset if the film hinge is molded onto a support which is aligned transversely to the plane of the base plate and for its part is in connection with the base plate by means of a further film hinge, because a displacement of the clamping clip is then possible without movement in the plane of the base plate.